Molecular dissection of the genes involved in A. fumigatus spore color synthesis and their role in virulence. Aspergillus is one of the most common fungal pathogens affecting neutropenic patients and other types of immunocompromised individuals such as those with Chronic granulomatous Disease of Childhood. Among a dozen species of Aspergillus reported to cause infection in humans, A. fumigatus is the most common species reported from invasive aspergillosis. All Aspergillus species propagate by conidia (spores), which humans encounter daily through inhalation. We have focused our attention on the molecular genetic aspects of conidial pigment biosynthesis since pigment is one of the visible components of the wall that protect conidia. In the previous years we have characterized the ARP1, ARP2 and ALB1 gene their products which are involved in 1,8-dihydroxynaphthalene (DHN) melanin biosynthesis. Furthermore, we have shown that the conidial pigment synthetic pathway plays an important role in pathogenesis. This year we have identified three additional genes, ABR1, ABR2 and AYG1, which are also involved in conidial pigment biosynthesis. Disruption of each of these genes resulted in alterations of conidial color. In addition, it was found that these six genes are clustered and developmentally regulated.